earth systems

• inner core

  Made of liquid iron and nickel
• crust

  This is the thinnest layer of the Earth
• outer core

  Made of slow moving, semi-molten rock
• mantle

  Made of rocks and minerals
• Why do plates move?

  1. The hot mantle nearest the core rises

  2. As it rises it cools

  3. This process is called convection

  4. The convection currents move the tectonic plates
• Earthquakes and volcanoes

  Tend to happen in the same places
• The Earth's surface is split into pieces called "tectonic plates"
• Where these plates meet are known as tectonic plate boundaries
• The plates are always moving
• They are moving very slowly, but they are moving, and every now and again, a build-up of pressure is released in the form of a sudden slip of the plates (earthquake) or an explosion of lava (volcano)
• Pangea

  A hypothetical supercontinent that included all current land masses, believed to have been in existence before the continents broke apart
• Earth's crust

  • Contains a lot of silicon, aluminium and magnesium
  • Solid, rigid
  • Ranges in temperature from 20-500°C
  • Continental crust is about 50 km thick, ocean crust is about 5-10 km thick
  • Average density of 2.9 g/ml
• Earth's mantle

  • Contains a lot of iron and magnesium silicates
  • Soft and consists of semi-molten rock called magma
  • Temperature of upper mantle is about 1000°C, lower mantle is about 2500°C
  • About 2900 km thick
  • Average density of about 3.6 g/ml
• Rocks are continually cycled
• Main types of rock

  • Igneous
  • Sedimentary
  • Metamorphic
• Igneous rocks


  Formed from molten rock that has cooled and solidified
• Igneous rocks


  • Obsidian (glasslike, very fast cooling on surface)
  • Pumice (gas bubbles, fast cooling on surface)
  • Basalt (small crystals, moderate cooling near surface)
  • Gabbro/Granite (large crystals, slow cooling in the Earth)
• Sedimentary rocks


  Formed when small particles of rock (sediment) build up and compact over time
• Sedimentary rocks

  • Crumbly and breaks away easily
  • Porous
  • Brittle/fragile
• How sedimentary rocks are formed

  1. When magma cools down and solidifies

  2. Sediment builds up and compacts over time
• Fossil

  The preserved remains or traces of a dead organism
• Fossilisation

  1. After an animal dies, the soft parts decompose leaving the hard parts behind

  2. The hard parts become buried by sediment

  3. As more sediment builds up, the sediment compacts and turns to rock

  4. Minerals in water replace the bones, leaving a rock replica
• Fossils display evidence of evolution
• Fossils of the simplest organisms are found in the oldest rocks, and fossils of more complex organisms in the newest rocks
• This supports the theory of evolution which states that simple life forms gradually evolved into more complex ones
• One theory suggests the early atmosphere came from intense volcanic activity, which released gases similar to the atmospheres of Mars and Venus today
• Atmospheres of Mars and Venus

  • Large amount of carbon dioxide
  • Little or no oxygen
  • Small amounts of other gases like ammonia and methane
• Volcanic activity also released water vapour, which condensed to form the oceans
• Nitrogen was probably also released by volcanoes and gradually built up in the atmosphere because it is unreactive
• For a long time, the percentage of carbon dioxide in the atmosphere remained a balancing act
• Processes involved in the recycling of carbon dioxide

  • Photosynthesis
  • Respiration
  • Feeding
  • Excretion
  • Death and decay
  • Fossilisation
  • Combustion
• How carbon is released

  1. Respiration: Glucose + Oxygen -> Water + Carbon Dioxide

  2. Combustion: Fuel + Oxygen -> Water + Carbon Dioxide
• How carbon is taken in


  1. Photosynthesis: Water + Carbon Dioxide -> Glucose + Oxygen

  2. Dissolving: Carbon Dioxide (gas) -> Carbon Dioxide (solution)